scholarly journals High-Precision Angle Prediction of Sun for Space Remote Sensing Instrument

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yan Wang ◽  
Zhanfeng Li ◽  
Guanyu Lin ◽  
Yu Huang
Keyword(s):  
Coordinate System ◽  
High Precision ◽  
Prediction Method ◽  
The Sun ◽  
Error Sources ◽  
Satellite Attitude ◽  
Satellite Platform ◽  
Conversion Matrix ◽  
Synchronous Orbit ◽  
Right Ascension

In order to grasp the timing of sun calibration in advance, this paper introduces a high-precision method to predict the solar angle by using the current broadcast time and orbital instantaneous root of the satellite platform. By calculating the sun’s apparent right ascension and apparent declination, the conversion matrix from the geocentric inertial coordinate system to the orbital coordinate system, and the satellite attitude correction matrix, the sun vector in the satellite body coordinate system is obtained. This method is used to predict the sun angle of a sun synchronous orbit in the satellite coordinate system, and the prediction results are compared with the STK simulation results. The results show that the sun angle prediction error of this method is less than ±0.003°. It can meet the requirements of on-orbit solar calibration. The main error sources in the prediction method are analysed.

scholarly journals A Precise Algorithm for Computing Sun Position on a Satellite

2019 ◽  
Author(s):  
Tao Zheng ◽  
Fei Zheng ◽  
Xi Rui ◽  
Xiang Ji
Keyword(s):  
Coordinate System ◽  
High Precision ◽  
Pitch Angle ◽  
Azimuth Angle ◽  
Maximum Deviation ◽  
The Sun ◽  
Solar Concentrator ◽  
The Difference ◽  
The One ◽  
Right Ascension

To meet the high precision sun tracking needs of a space deployable membrane solar concentrator and other equipment, an existing algorithm for accurately computing the sun position is improved. Firstly, compared with other theories, the VSOP (variation seculaires des orbits planetaires) 87 theory is selected and adopted to obtain the sun position in the second equatorial coordinate system. Comparing the results with data of the astronomical almanac from 2015, it is found that the deviation of the apparent right ascension does not exceed 0.17 arc seconds, while that of the apparent declination does not exceed 1.2 arc seconds. Then, to eliminate the difference in the direction of the sun position with respect to the satellite caused by the size of the satellite’s orbit, a translation transform is introduced in the proposed algorithm. Finally, the proposed algorithm is applied to the orbit of the satellite designated by SJ-4 (shijian-4). Under the condition that both of the existing and improved algorithms adopt the VSOP87 theory to compute sun position in the second equatorial coordinate system, the maximum deviation of the azimuth angle on the SJ-4 is 35.19 arc seconds and the one of pitch angle is 19.93 arc seconds, when the deviation is computed by subtracting the results given by both algorithms. In summary, the proposed algorithm is more accurate than the existing one.

scholarly journals Evolution of space debris for spacecraft in the Sun-synchronous orbit

2020 ◽  
Vol 29 (1) ◽  
pp. 265-274
Author(s):  
Yu Jiang ◽  
Hengnian Li ◽  
Yue Yang
Keyword(s):  
Space Debris ◽  
Rate Of Change ◽  
The Sun ◽  
Orbital Parameters ◽  
Velocity Error ◽  
Synchronous Orbit ◽  
The Right ◽  
The Impact ◽  
Impact Motion ◽  
Right Ascension

AbstractIn this paper, the evolution of space debris for spacecraft in the Sun-Synchronous orbit has been investigated. The impact motion, the evolution of debris from the Sun-Synchronous orbit, as well as the evolution of debris clouds from the quasi-Sun-Synchronous orbit have been studied. The formulas to calculate the evolution of debris objects have been derived. The relative relationships of the velocity error and the rate of change of the right ascension of the ascending node have been presented. Three debris objects with different orbital parameters have been selected to investigate the evolution of space debris caused by the Sun-Synchronous orbit. The debris objects may stay in quasi-Sun-Synchronous orbits or non-Sun-Synchronous orbits, which depend on the initial velocity errors of these objects.

Fundamental observations made at Breslau in 1922-1925

1978 ◽  
Vol 48 ◽  
pp. 433-435
Author(s):  
F. Schmeidler
Keyword(s):  
The Sun ◽  
Vertical Circle ◽  
Right Ascension

Meridian observations of fundamental stars were made at Breslau Observatory in 1922 to 1925. The observations in right ascension were made by W.Rabe with the 6-inch transit instrument, whereas the declinations were observed by A.Wilkens with the vertical circle. In both coordinates, observations of the Sun were also made.

Modelling Lunar Extremes

2018 ◽  
Vol 3 (2) ◽  
pp. 207-216 ◽  
Author(s):  
David Fisher ◽  
Lionel Sims
Keyword(s):  
High Precision ◽  
Celestial Mechanics ◽  
Computer Modelling ◽  
Landscape Context ◽  
The Sun ◽  
The Moon

Claims first made over half a century ago that certain prehistoric monuments utilised high-precision alignments on the horizon risings and settings of the Sun and the Moon have recently resurfaced. While archaeoastronomy early on retreated from these claims, as a way to preserve the discipline in an academic boundary dispute, it did so without a rigorous examination of Thom’s concept of a “lunar standstill”. Gough’s uncritical resurrection of Thom’s usage of the term provides a long-overdue opportunity for the discipline to correct this slippage. Gough (2013), in keeping with Thom (1971), claims that certain standing stones and short stone rows point to distant horizon features which allow high-precision alignments on the risings and settings of the Sun and the Moon dating from about 1700 BC. To assist archaeoastronomy in breaking out of its interpretive rut and from “going round in circles” (Ruggles 2011), this paper evaluates the validity of this claim. Through computer modelling, the celestial mechanics of horizon alignments are here explored in their landscape context with a view to testing the very possibility of high-precision alignments to the lunar extremes. It is found that, due to the motion of the Moon on the horizon, only low-precision alignments are feasible, which would seem to indicate that the properties of lunar standstills could not have included high-precision markers for prehistoric megalith builders.

scholarly journals Solar barycentric dynamics from a new solar-planetary ephemeris

2018 ◽  
Vol 615 ◽  
pp. A153 ◽  
Author(s):  
Rodolfo G. Cionco ◽  
Dmitry A. Pavlov
Keyword(s):  
High Precision ◽  
Orbital Motion ◽  
Giant Planets ◽  
Reference Plane ◽  
The Sun ◽  
The Future ◽  
Dynamical Parameters ◽  
Definition Of ◽  
Invariable Plane ◽  
Planetary Theories

Aims. The barycentric dynamics of the Sun has increasingly been attracting the attention of researchers from several fields, due to the idea that interactions between the Sun’s orbital motion and solar internal functioning could be possible. Existing high-precision ephemerides that have been used for that purpose do not include the effects of trans-Neptunian bodies, which cause a significant offset in the definition of the solar system’s barycentre. In addition, the majority of the dynamical parameters of the solar barycentric orbit are not routinely calculated according to these ephemerides or are not publicly available. Methods. We developed a special version of the IAA RAS lunar–solar–planetary ephemerides, EPM2017H, to cover the whole Holocene and 1 kyr into the future. We studied the basic and derived (e.g., orbital torque) barycentric dynamical quantities of the Sun for that time span. A harmonic analysis (which involves an application of VSOP2013 and TOP2013 planetary theories) was performed on these parameters to obtain a physics-based interpretation of the main periodicities present in the solar barycentric movement. Results. We present a high-precision solar barycentric orbit and derived dynamical parameters (using the solar system’s invariable plane as the reference plane), widely accessible for the whole Holocene and 1 kyr in the future. Several particularities and barycentric phenomena are presented and explained on dynamical bases. A comparison with the Jet Propulsion Laboratory DE431 ephemeris, whose main differences arise from the modelling of trans-Neptunian bodies, shows significant discrepancies in several parameters (i.e., not only limited to angular elements) related to the solar barycentric dynamics. In addition, we identify the main periodicities of the Sun’s barycentric movement and the main giant planets perturbations related to them.

scholarly journals XXVIII. On the discordances between the sun's observed and computed right ascensions, as determined at the Blackman-street observatory, in the years 1821 and 1822; with experiments to show that they did not originate in instrumental derangement. also a description of the seven-feet transit with which the observations were procured, and upon which the experiments were made

1826 ◽  
Vol 116 ◽  
pp. 423-483 ◽  
Keyword(s):  
Royal Society ◽  
The Sun ◽  
Accurate Knowledge ◽  
The Subject ◽  
Right Ascension ◽  
Solar Rays

In presenting to the Royal Society the following pages, I am well aware that some apology is necessary; the subject however to which they refer being intimately connected with the progress of astronomy, I am induced to hope that the Society will still receive with indulgence, what would long since have been communicated to them, had other astronomical pursuits allowed me the opportunity. That the sun's right ascension, found by observation , frequently disagrees with that afforded by calculation , astronomers I believe now generally admit; an opinion however has been as generally entertained, that the discordances were the results of instrumental inaccuracy, occasioned by the effects of the solar rays upon certain parts of the instrument; hence observations of the sun have fallen into disrepute, whenever an accurate knowledge of the time is the object of research.

scholarly journals Visual-Inertial Odometer-Based Global High Precision Indoor Human Navigation in a University Library

2019 ◽  
Vol 1 ◽  
pp. 1-2
Author(s):  
Shinpei Ito ◽  
Akinori Takahashi ◽  
Ruochen Si ◽  
Masatoshi Arikawa
Keyword(s):  
Coordinate System ◽  
High Precision ◽  
Real World ◽  
Indoor Navigation ◽  
Experimental Result ◽  
Coordinate Space ◽  
Central Position ◽  
Global Coordinate System ◽  
Prototype System ◽  
3D Environments

<p><strong>Abstract.</strong> AR (Augmented Reality) could be realized as a basic and high-level function on latest smartphones with a reasonable price. AR enables users to experience consistent three-dimensional (3D) spaces co-existing with 3D real and virtual objects with sensing real 3D environments and reconstructing them in the virtual world through a camera. The accuracy of sensing real 3D environments using an AR function, that is, visual-inertial odometer, of a smartphone is extremely higher than one of a GPS receiver on it, and can be less than one centimeter. However, current common AR applications generally focus on “small” real 3D spaces, not large real 3D spaces. In other words, most of the current AR applications are not designed for uses based on a geographic coordinate system.</p><p>We proposed a global extension of the visual-inertial odometer with an image recognition function of geo-referenced image markers installed in real 3D spaces. Examples of geo-referenced image markers can be generated from analog guide boards existing in the real world. We tested this framework of a global extension of the visual-inertial odometer embedded in a smartphone on the first floor in the central library of Akita University. The geo-referenced image markers such as floor map boards and book categories sign boards were registered in a database of 3D geo-referenced real-world scene images. Our prototype system developed on a smartphone, that is, iPhone XS, Apple Inc., could first recognized a floor map board (Fig. 1), and could determine the 3D precise distance and direction of the smartphone from the central position of the floor map board in a local 3D coordinate space with the origin point as the central positon of the board. Then, the system could convert the relative precise position and the relative direction of the smartphone’s camera in a local coordinate space into a global precise location and orientation of it. A subject was walking the first floor in the building of the library with a world tracking function of the smartphone. The experimental result shows that the error of tracking a real 3D space of a global coordinate system was accumulated, but not bad. The accumulated error was only about 30 centimeters after the subject’s walking about 30 meters (Fig. 2). We are now planning to improve our prototype system in the accuracy of indoor navigation with calibrating the location and orientation of a smartphone based sequential recognitions of multiple referenced scene image markers which have already existed for a general user services of the library before developing this proposed new services. As the conclusion, the experiment’s result of testing our prototype system was impressive, we are now preparing a more practical high-precision LBS which enables a user to be navigated to the exact location of a book of a user’s interest in a bookshelf on a floor with AR and floor map interfaces.</p>

scholarly journals IV.On a supposed alteration in the amount of astronomical aberration of light, produced by the passage of the light through a considerable thickness of refracting medium

1872 ◽  
Vol 20 (130-138) ◽  
pp. 35-39 ◽  
Keyword(s):  
Royal Academy ◽  
Angular Displacement ◽  
Focal Length ◽  
The Sun ◽  
Change Of Direction ◽  
The Subject ◽  
The Difference ◽  
North Polar ◽  
Academy Of Sciences ◽  
Right Ascension

A discussion has taken place on the Continent, conducted partly in the 'Astronomische Nachrichten,’ partly in independent pamphlets, on the change of direction which a ray of light will receive (as inferred from the Undulatory Theory of Light) when it traverses a refracting medium which has a motion of translation. The subject to which attention is particularly called is the effect that will be produced on the apparent amount of that angular displacement of a star or planet which is caused by the Earth’s motion of translation, and is known as the Aberration of Light. It has been conceived that there may be a difference in the amounts of this displacement, as seen with different telescopes, depending on the difference in the thicknesses of their object-glasses. The most important of the papers containing this discussion are:—that of Professor Klinkerfues, contained in a pamphlet published at Leipzig in 1867, August; and those of M. Hoek, one published 1867, October, in No. 1669 of the 'Astronomische Nachrichten,’ and the other published in 1869 in a communication to the Netherlands Royal Academy of Sciences. Professor Klinkerfues maintained that, as a necessary result of the Undulatory Theory, the amount of Aberration would be increased, in accordance with a formula which he has given; and he supported it by the following experiment:— In the telescope of a transit-instrument, whose focal length was about 18 inches, was inserted a column of water 8 inches in length, carried in a tube whose ends were closed with glass plates; and with this instrument he observed the transit of the Sun, and the transits of certain stars whose north-polar distances were nearly the same as that of the Sun, and which passed the meridian nearly at midnight. In these relative positions, the difference between the Apparent Right Ascension of the Sun and those of the stars is affected by double the coefficient of Aberration; and the merely astronomical circumstances are extremely favourable for the accurate testing of the theory. Professor Klinkerfues had computed that the effect of the 8-inch column of water and of a prism in the interior of the telescope would be to increase the coefficient of Aberration by eight seconds of arc. The observation appeared to show that the Aberration was really increased by 7'' 1. It does not appear that this observation was repeated.

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